West Lake Sammamish Weather in September

What's the weather like in West Lake Sammamish (Washington) in September 2025?

The climate in West Lake Sammamish during September can be summarized as mild and reasonably dry.

September is in the fall / autumn in West Lake Sammamish and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 20°C (69°F), whilst at night 10°C (50°F) is normal.

West Lake Sammamish weather averages (imperial / metric)
Daytime temperature 20.3°C 68.5°F
Nightly temperature 9.7°C 49.5°F
Average temperature 15°C 59°F
Daily sunshine 7.8 hrs
Avg rainfall 66 mm 2.6 ins
Rainy days 9 days
Sea temperature 12.8°C 55.1°F
Humidity 72%
Windspeed 11.9kph 7 mph

On average September is the 4th driest month of the year in West Lake Sammamish with around 66mm 2.6 inches of rain making it a reasonably dry time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 7.8 hours of sunshine per day.

September temperatures in West Lake Sammamish

West Lake Sammamish average temperature in September

September rainfall

West Lake Sammamish average rain in September

September hourly sunshine

West Lake Sammamish average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in West Lake Sammamish in September 2025.

Other monthly averages

Best places to visit in September

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Current (hourly) weather 15 day forecast

West Lake Sammamish weather stats

West Lake Sammamish weather statistics
Hottest month: July 23.1°C 73.6°F
Driest month: July 30mm 1.2ins
Sunniest month: July 10.8hrs
Coldest month: January 6.7°C 44.1°F
Wettest month: December 186mm 7.3ins
Map showing location of West Lake Sammamish (47.5776, -122.10123) West Lake Sammamish map pin © Google

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